
String conversion and formatting
********************************

Functions for number conversion and formatted string output.

int PyOS_snprintf(char *str, size_t size, const char *format, ...)

   Output not more than *size* bytes to *str* according to the format
   string *format* and the extra arguments. See the Unix man page
   *snprintf(2)*.

int PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va)

   Output not more than *size* bytes to *str* according to the format
   string *format* and the variable argument list *va*. Unix man page
   *vsnprintf(2)*.

``PyOS_snprintf()`` and ``PyOS_vsnprintf()`` wrap the Standard C
library functions ``snprintf()`` and ``vsnprintf()``. Their purpose is
to guarantee consistent behavior in corner cases, which the Standard C
functions do not.

The wrappers ensure that *str*[*size*-1] is always ``'\0'`` upon
return. They never write more than *size* bytes (including the
trailing ``'\0'`` into str. Both functions require that ``str !=
NULL``, ``size > 0`` and ``format != NULL``.

If the platform doesn't have ``vsnprintf()`` and the buffer size
needed to avoid truncation exceeds *size* by more than 512 bytes,
Python aborts with a *Py_FatalError*.

The return value (*rv*) for these functions should be interpreted as
follows:

* When ``0 <= rv < size``, the output conversion was successful and
  *rv* characters were written to *str* (excluding the trailing
  ``'\0'`` byte at *str*[*rv*]).

* When ``rv >= size``, the output conversion was truncated and a
  buffer with ``rv + 1`` bytes would have been needed to succeed.
  *str*[*size*-1] is ``'\0'`` in this case.

* When ``rv < 0``, "something bad happened." *str*[*size*-1] is
  ``'\0'`` in this case too, but the rest of *str* is undefined. The
  exact cause of the error depends on the underlying platform.

The following functions provide locale-independent string to number
conversions.

double PyOS_string_to_double(const char *s, char **endptr, PyObject *overflow_exception)

   Convert a string ``s`` to a ``double``, raising a Python exception
   on failure.  The set of accepted strings corresponds to the set of
   strings accepted by Python's ``float()`` constructor, except that
   ``s`` must not have leading or trailing whitespace. The conversion
   is independent of the current locale.

   If ``endptr`` is ``NULL``, convert the whole string.  Raise
   ValueError and return ``-1.0`` if the string is not a valid
   representation of a floating-point number.

   If endptr is not ``NULL``, convert as much of the string as
   possible and set ``*endptr`` to point to the first unconverted
   character.  If no initial segment of the string is the valid
   representation of a floating-point number, set ``*endptr`` to point
   to the beginning of the string, raise ValueError, and return
   ``-1.0``.

   If ``s`` represents a value that is too large to store in a float
   (for example, ``"1e500"`` is such a string on many platforms) then
   if ``overflow_exception`` is ``NULL`` return ``Py_HUGE_VAL`` (with
   an appropriate sign) and don't set any exception.  Otherwise,
   ``overflow_exception`` must point to a Python exception object;
   raise that exception and return ``-1.0``.  In both cases, set
   ``*endptr`` to point to the first character after the converted
   value.

   If any other error occurs during the conversion (for example an
   out-of-memory error), set the appropriate Python exception and
   return ``-1.0``.

   New in version 2.7.

double PyOS_ascii_strtod(const char *nptr, char **endptr)

   Convert a string to a ``double``. This function behaves like the
   Standard C function ``strtod()`` does in the C locale. It does this
   without changing the current locale, since that would not be
   thread-safe.

   ``PyOS_ascii_strtod()`` should typically be used for reading
   configuration files or other non-user input that should be locale
   independent.

   See the Unix man page *strtod(2)* for details.

   New in version 2.4.

   Deprecated since version 2.7: Use ``PyOS_string_to_double()``
   instead.

char* PyOS_ascii_formatd(char *buffer, size_t buf_len, const char *format, double d)

   Convert a ``double`` to a string using the ``'.'`` as the decimal
   separator. *format* is a ``printf()``-style format string
   specifying the number format. Allowed conversion characters are
   ``'e'``, ``'E'``, ``'f'``, ``'F'``, ``'g'`` and ``'G'``.

   The return value is a pointer to *buffer* with the converted string
   or NULL if the conversion failed.

   New in version 2.4.

   Deprecated since version 2.7: This function is removed in Python
   2.7 and 3.1.  Use ``PyOS_double_to_string()`` instead.

char* PyOS_double_to_string(double val, char format_code, int precision, int flags, int *ptype)

   Convert a ``double`` *val* to a string using supplied
   *format_code*, *precision*, and *flags*.

   *format_code* must be one of ``'e'``, ``'E'``, ``'f'``, ``'F'``,
   ``'g'``, ``'G'`` or ``'r'``.  For ``'r'``, the supplied *precision*
   must be 0 and is ignored.  The ``'r'`` format code specifies the
   standard ``repr()`` format.

   *flags* can be zero or more of the values *Py_DTSF_SIGN*,
   *Py_DTSF_ADD_DOT_0*, or *Py_DTSF_ALT*, or-ed together:

   * *Py_DTSF_SIGN* means to always precede the returned string with a
     sign character, even if *val* is non-negative.

   * *Py_DTSF_ADD_DOT_0* means to ensure that the returned string will
     not look like an integer.

   * *Py_DTSF_ALT* means to apply "alternate" formatting rules.  See
     the documentation for the ``PyOS_snprintf()`` ``'#'`` specifier
     for details.

   If *ptype* is non-NULL, then the value it points to will be set to
   one of *Py_DTST_FINITE*, *Py_DTST_INFINITE*, or *Py_DTST_NAN*,
   signifying that *val* is a finite number, an infinite number, or
   not a number, respectively.

   The return value is a pointer to *buffer* with the converted string
   or *NULL* if the conversion failed. The caller is responsible for
   freeing the returned string by calling ``PyMem_Free()``.

   New in version 2.7.

double PyOS_ascii_atof(const char *nptr)

   Convert a string to a ``double`` in a locale-independent way.

   See the Unix man page *atof(2)* for details.

   New in version 2.4.

   Deprecated since version 3.1: Use ``PyOS_string_to_double()``
   instead.

char* PyOS_stricmp(char *s1, char *s2)

   Case insensitive comparison of strings. The function works almost
   identically to ``strcmp()`` except that it ignores the case.

   New in version 2.6.

char* PyOS_strnicmp(char *s1, char *s2, Py_ssize_t  size)

   Case insensitive comparison of strings. The function works almost
   identically to ``strncmp()`` except that it ignores the case.

   New in version 2.6.
